Research On Theories Of Mobile Linkage With Multiple Locomotion Modes

With the development of the technologies of mobile robots, the working environments are becoming more and more complex (such as planet explorations and earthquake search and rescue), and the locomotion modes are also extended from one single mode to multiple modes. To significantly improve the capabilities of mobile robot in unknown environments, hybrid, slef-reconfigurable and other new types of mobile platforms are presented. In a view of mechanism, a mobile robot can be considered as a kind of mobile linkage. Therefore, the mobile abilities can be enhanced due to the dramatic deformations and mobilities of linkages. In this thesis, we firstly put forward the idea of mobile linkage with multiple locomotion modes, which has mobile ability at any gesture. It is a kind of cooled-loop mechanism with complex deformation ability, multiple locomotion modes (such as rolling, snake-like, wheeled or legged motions etc.) and can be integrated and switched by its deformations and multi-modal motions. Based on this idea, parallelogram linkage, planar and spatial closed-loop linkages are designed and their locomotion modes are further studied respectively. The researches mainly contain(1) Based on a single parallelogram linkage, the singularity positions are controlled by a redundant motor to change its sates between parallelogram and anti-parallelogram states. Through kinematic and dynamic analysis, sliding, crawling and tumbling modes are presented. Further, using crawling and tumbling gaits, two methods of turning function for a single DOF mechanism are proposed respectively.(2) Using the methods of foldable Bricard linkage and metamorphic mechanism, a kind of eight-bar mobile linkage is presented, which can be switched its states between planar parallelogram mechanism (PPM) and spherical four-bar mechanism (SFM). Based on the ZMP analysis, two rolling modes are further presented. Combining the two modes, the mechanism can roll and change its mobile directions freely on flat ground.(3) A class of single DOF multi-loop linkages with a central actuated link is constructed following central symmetry principle. Based on ZMP analysis, the rolling modes and gaits are obtained. Furthermore, a self-balancing position of this type of linkages is introduced. Using this position, a passive rolling-walking mode is further realized.(4) An equivalent tetrahedral unit composed of a tripod linkage is proposed.Then, a class of mobile linkages with regular polyhedral shapes is constructed with the units. The design method and the approach of locomotion analysis are studied. Taking two units (Triangular-bipyramid mechanism) as an example, the principle and the locomotion modes are introduced.(5) For the single DOF TBM constructed by the method in section 5, two types of rolling mode are presented (definite rolling and random rolling mode). Based on the two modes, a method of turning of the single DOF TBM and its corresponding control strategy are introduced. Further, a simulation program is performed to verify the validity of the function. According to, this method, it is possible to make a single DOF mechanism to roll to any position on flat ground.(6) Integrating the principle of parallel, foldable and reconfigurable mechanisms, three types of mobile linkages are presented and their deformations and locomotion modes are further analyzed using the idea of multiple operation modes. First, a kind of mobile 3-RSR parallel mechanism is proposed. Using the analysis method in section 4, the rolling modes of the mechanism at all supporting states are studied. Second, based on the mobile 3-RSR parallel mechanism, each of the platforms of parallel mechanism is constructed as a foldable mechanism with single DOF to improve the operation modes of platforms. Worm-like, self-crossing and rolling modes are obtained according to the deformation analysis. Third, a design method of a chain of parallel mechanism and its deformation technology is presented. The chain can be changed into a serial mechanism using its metamorphic and singularity characteristics.Further, using this technology, a design method of a parallel mechanism can be deformed into a legged robot is introduced. Based on the motion analysis of platforms and deformations of chains, rolling, tumbling, eccentric wheel and legged locomotion modes are introduced. The rapid switching function between these modes is also discussed. It can be seen that this part of research successfully describes the idea of this thesis and combine rolling, wheeled and legged locomotion modes (three efficient modes) on a single mechanism. This method can highly improve the mobile abilities of the mechanism, and will be the supporting and key technology for designing excellent mobile robot with high adaptability and strong terrainability.